At least 20 to 30 percent of paients with sickle cell disease have abnormal amounts of protein excretion in their urine, and 6 to 18 percent have renal insufficiency. Angiotensin II converting enzyme inhibitors (ACE1s) have been shown to reduce proteinuria in patients with renal biopsy proven sickle cell nephropathy when given for a short interval. This is a randomized, prospective, placebo controlled study analyzing the effects of an ACE1 when compared to placebo in patients with sickle cell nephropathy. The study was designed to answer two questions: 1) Does the long term administration of an ACE1 reduce proteinuria, and 2) can ACE1 therapy prevent or retard the development of renal insufficiency in patients with sickle cell anemia? A total of 20 subjects will be studied. Subjects will take either the ACE1 or placebo for three years. The patients will be monitored, blood will be drawn, and a 24-hour urine will be evaluated at entry and at 1, 3, 6, 12, 18, 24, 30 and 36 months. The main outcomes of 24 hour urine protein, creatinine clearance, serum creatinine will be evaluated statistically using repeated measure techniques to see if the ACE1 group has a more favorable outcome than the placebo treated group. To date, two patients have been enrolled at UAB. One patient, randomized to the placebo arm, died of a gastrointestinal related illness. The other tolerated ACE1 poorly due to the development of hyperkalemia. Data from the entire study are being analyzed by the Suke/UNC Comprehensive Sickle Cell Center.